In the 15 years since herbicide-resistant crops were first introduced, weeds already have become resistant to herbicides affiliated with genetically engineered crops. In particular, application of Monsanto’s Roundup has spawned glyphosate-resistant weeds, a problem that is driving farmers to apply older, more toxic herbicides and to reduce conservation tilling to combat weeds. Now, to treat the problem of glyphosate-resistant weeds, biotechnology companies are simply creating crops resistant to a variety of chemicals.

Dow AgroScience’s variety of corn up for USDA approval, DAS-40278-9, is resistant to ACCase inhibitor herbicides (including quizalofop, which is not registered for use on corn) as well as 2,4-D. The chemical 2,4-Dichlorophenoxyacetic acid (2,4-D) once made up half of the herbicide mix known as Agent Orange. Corn with 2,4-D resistance could be dangerous to eat because a metabolite of 2,4-D is known to cause skin sores, liver damage and sometimes death in animals. 2,4-D is a potential endocrine disruptor and can affect development. Rats exposed to 2,4-D exhibited depressed thyroid hormone levels, which can affect normal metabolism and brain functioning. Studies found that men who applied 2,4-D had lower sperm counts and more sperm abnormalities than those unexposed to the herbicide.

Not only is 2,4-D dangerous for human health, but it also spurs weed resistance. According to the International Survey of Herbicide Resistant Weeds, there have been 29 weeds found to be resistant to 2,4-D’s family of synthetic auxin herbicides. It is only a matter of time before Dow stacks this variety with glyphosate-resistance, which could lead to situations where Roundup and 2,4-D are sprayed on the same crop.

The chemical treadmill model cannot be continued indefinitely. Weed resistance to these chemicals will continue to abound and the application of more noxious herbicides will increase exponentially. This new corn variety is not only unsafe and inefficient, but it is a completely unsustainable solution to the broader problem of high-input production agriculture and associated environmental pressures.

Unsafe to Eat

Although FDA considers Dow’s 2,4-D corn, “as safe as conventional corn varieties…and not materially different” from corn currently grown and marketed in the United States, the FDA’s Biotechnology Consultation Note for 2,4-D-resistant corn lists several amino acids, fatty acids, vitamins and minerals that differed from conventional corn and were statistically significant, including glutamic acid, oleic acid, vitamin C and zinc. A description of differences without data showing that these differences are “safe” is inadequate, especially when scientists from the French National Institute for Agricultural Research suggest that “following 2,4-D treatment, 2,4-D tolerant plants may not be acceptable for human consumption.”

Harmful for the Environment

On February 23, 2012, the National Resources Defense Council (NRDC) filed a lawsuit against the EPA for failing to respond to a 2008 petition to cancel registration of 2,4-D, citing its common use despite links to cancer, cell damage, reproductive problems and non-Hodgkin’s lymphoma. With the approval of 2,4-D resistant corn, NRDC claims that use of 2,4-D could grow 50-fold.

Aside from its harmful endocrine and carcinogenic effects, 2,4-D is a very volatile herbicide, which can easily drift onto nearby crops, vegetables and flowers. In fact, a comparative risk assessment found that 2,4-D was 400 times more likely to cause non-target plant injury than glyphosate (also known as Roundup, the herbicide many currently used GE crops are engineered to survive.) In an Association of American Pesticide Control Officials (AAPCO) survey on pesticide drift, 2,4-D was the herbicide most commonly involved in drift occurrences. The drift potential of 2,4-D is a concern for ecosystems containing sensitive organisms since the EPA’s toxicity research found 2,4-D to be “very highly toxic to slightly toxic to freshwater and marine invertebrates.”

The USDA claims that planting 2,4-D crops and using more 2,4-D will not adversely impact the listed endangered species or their critical habitats, when in fact, it certainly will. In 2009, the EPA issued a determination on the risks of 2,4-D use to the California Red-legged Frog and the Alameda Whipsnake and concluded that 2,4-D is likely to adversely affect and modify the designated critical habitat of both species.Additionally, in March 2011, the National Marine Fisheries Services (NMFS) released its Draft Biological Opinions and concluded that, “the proposed registration of pesticides containing 2,4-D…are likely to jeopardize the continued existence of one or more of the 28 endangered and threatened Pacific salmonids and 2,4-D are likely to adversely modify or destroy the designated critical habitat for one or more of the 28 threatened and endangered salmonids.”

All of the human safety and environmental risks associated with 2,4-D use beg the question—why approve 2,4-D ready corn? The answer: Dow expects to reap in $1.5 billion in extra profit in 2013 from 2,4-resistant corn sales alone.

The dangers of 2,4-D can no longer be neglected—The USDA should not approve Dow’s 2,4-D resistant corn and EPA should ban the use of 2,4-D in the United States.

The good news? In May 2013, the USDA announced that it would be doing environmental impact statements for crops tolerant to 2,4-D and dicamba, a related herbicide. This more rigorous review of the chemicals is good news and shows that the USDA can be pressured to do the right thing if enough people speak up.